The invention relates to an adjustment device for adjusting for the wearing of brake pads in a disc brake, in particular in a pneumatically actuated disc brake.
Different types of wear adjustment devices for disc brakes are known. There are, for example, wear adjustment devices for pneumatically actuated disc brakes, in particular for such pneumatic brakes having a sliding caliper, and for pneumatically actuated fixed or pivoting caliper disc brakes.
Pneumatically actuated disc brakes are now standard equipment in heavy commercial vehicles. Disc brakes of this type require a device for adjusting pad wear. The prior art is an automatically operating wear adjustment, by means of which it is achieved that what is known as the air play, which means the gap between the brake pads and the brake disk in the non-actuated state, is kept constant independently of the wear state and wear behavior of the brake pads.
Disc brakes are found very frequently in commercial vehicles, which disc brakes have a wear adjuster which is arranged concentrically in the cavity of a threaded spindle and is driven eccentrically by the brake lever via a drive element (for example, a shifting finger, or a gearwheel).
In adjustment devices of this type, different overload and coupling devices are provided which can transmit and limit torques which are necessary for actuating the adjustment device (for example, adjusting, resetting, slipping when stops are reached).
An overload and coupling device of this type frequently has a friction combination with at least two contact faces which are in contact. The friction combination is also called a tribological functional unit.
Adjustment devices of this type can have at least one friction combination.
DE 102004037771 A1 (having U.S. counterpart U.S. Pat. No. 7,926,626 B2) illustrates one example.
There is a need for an improved adjustment device as a result of the increased requirements with regard to economy of production and quality (maintenance intervals), a defined position within an installation space which is as small as possible, and increased strength.
It is therefore the object of the present invention to provide an improved adjustment device.
Accordingly, an adjustment device is provided for adjusting wear of the brake pads and brake disk of a disc brake, in particular a pneumatically actuated disc brake having a brake application device which is actuated by a rotary lever. The adjusting device can preferably be inserted into an actuating spindle of the brake application device, and can be attached to a brake caliper of the disc brake by way of a bearing plate. The adjusting device has a spindle and at least one friction combination with, in each case, two contact faces. The adjustment device is distinguished by the fact that the at least one friction combination has a curved cross section of at least one of the contact faces.
The curved cross section of at least one of the contact faces of the at least one friction combination makes lower fluctuation possible of a torque which can be transmitted by means of the friction combination or of a torque limit, since a wide-area contact of the contact faces with the formation of what are known as edge loadings is prevented on account of the curved shape. More precise fixing of the torque is possible.
It is provided in one embodiment that the curved cross section of at least one of the contact faces has at least one elevation with an effective radius. The effective radius can thus not lie at an approximately 25% geometrically induced fluctuation as in the case of flat contact faces between an inner effective radius, for example of 7.5 mm, and an outer effective radius, for example of 10 mm, but rather can be defined more precisely, that is to say, in a geometrically unambiguous manner.
To this end, the curved cross section of at least one of the contact faces is of a convex configuration in one preferred embodiment.
It can be achieved in this way that, after running-in/wear processes, spacings on both sides from the effective radius radially to the outside and to the inside are produced uniformly, as a result of which more precise fixing of the torque, which is transmitted by way of the friction combination, is possible within narrower tolerances than in the prior art by way of planar contact faces.
In a further embodiment, a spindle contact face of the spindle and a contact face of a spherical disk with a spherical section face form the at least one friction combination. The spherical disk makes contact by way of the spherical section face with the bearing plate.
In one embodiment, the spherical disk can have the at least one contact face with the curved cross section. The manufacturing options for the spherical disks can also be adapted or extended simply for the curved cross section.
It is provided here that the spherical disk includes a spherical layer, a carrier section and a spherical disk contact section. The spherical disk contact section is arranged so as to lie opposite the spherical layer and has the at least one contact face with the curved cross section. The spherical disk can be constructed in one piece, or else from two or more components.
In a further embodiment, the spherical disk is provided with a passage which extends axially through the spherical layer and communicates with a hollowed-out portion of the carrier section. The spindle of the adjustment device can extend through the passage. An alignment of the spherical disk with respect to the spindle also is possible.
In another embodiment, an axial passage length of the passage can correspond substantially to an axial layer thickness of the spherical layer.
In another embodiment, at least one of the contact faces can be surface-treated, as a result of which it is additionally possible to influence the friction combination and, therefore, the torque which can be transmitted.
In another embodiment, the spindle contact face of the spindle can have the at least one contact face with the curved cross section. This can also be possible in addition to the contact face of the spherical disk. As a result, simple broadening of the area of use can be made possible.
A disc brake, in particular a pneumatically actuated disc brake, is provided with at least one above-described adjustment device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.